Electro-absorption modulators (EAMs) and electro-absorption modulated lasers (EMLs) are useful for transmitting information in telecommunications or data communication systems. EMLs have several advantages over other modulation sources. For example, EMLs can directly generate communication signals with relatively low bit-error rates without the use of external filters, which are undesirable because they are relatively large and expensive. External filters also occupy valuable space on the transmitter electronics board. In addition, EMLs directly generate transmission characteristics that have a relatively “clean” eye pattern when viewed on a communication signal analyzer. Such an eye pattern indicates acceptable discrimination between a digital “1” and digital “0” and, therefore, a relatively error-free (i.e. a bit error rate of less than 10−9) information transmission.
Another advantage of EMLs is that they can generate a stable and high-power modulated light beam. Yet another advantage of EMLs is that they can generate optical signals that are modulated at relatively high data rates. In addition, an EML is convenient to use because it is relatively easy to mount an EML in a package with an industry standard input impedance, which can be impedance matched to numerous commercially available drive voltage sources. EMLs are also relatively inexpensive.
A disadvantage of common, currently available EMLs, however, is that they require external thermal controllers for many practical applications. For example, EMLs require external thermal controllers, such as thermoelectric coolers (TECs), to maintain the EMLs at a substantially constant operating temperature so that data transmission can occur relatively error-free even as ambient temperatures vary over a relatively large range, e.g., over the entire Synchronous Optical Network (SONET) standardized operating temperature range. In general, external thermoelectric coolers are undesirable because they are power-intensive, relatively large and relatively expensive devices.